As you know, Windows 10 will be offered as a free upgrade for Windows 7 and 8.1 users within the first year after launch and the OS will be supported by providing updates and improvements during the whole lifetime of your device. Microsoft has now started showing 'Windows 10 upgrade notifications' on computers running Windows 7 and Windows 8.1 and the company allows users to reserve their free copy of Windows 10.

The notification will appear after installing update KB3035583 via Windows Update. It's a small app which prompt to enter your email address. This simple step will reserve your free copy of Windows 10 which will auto-download when it is ready.